Genetics of Pendred Syndrome

Pendred syndrome is characterized by children experiencing early hearing loss. This genetic disorder may also affect the patient's balance and their thyroid gland. Children born with this disorder may begin to lose their hearing as early as birth or by around three years of age.

The hearing loss associated with this disorder is progressive and some will experience total deafness. Almost everyone with this disorder will experience hearing loss in both ears, however, one ear often has more hearing loss than the other. The hearing loss most often occurs suddenly and in stages.

Understanding the genetics of Pendred syndrome helps patients and health care providers better understand this disorder. This disorder is actually a common form of deafness and of all cases of hereditary hearing loss, this disorder accounts for about ten percent. However, it is unknown exactly how many people are affected.

Roughly one-half of all patients affected with the familial form have an SLC26A4 gene mutation. This gene is responsible for producing the instructions necessary for creating pendrin, a protein. This protein is responsible for the transport of negatively charged ions, including bicarbonate, iodide, and chloride, out of and into cells. Pendrin's exact function is not completely understood, but it is known that it is important for normal inner ear and thyroid function. When this gene is mutated, the function or structure of pendrin is altered, resulting in ion transport disruptions. In some cases, the cause of this disorder is not known. Through understanding the genetics of Pendred syndrome, it is known that it is inherited in an autosomal recessive pattern.

This disorder may affect the thyroid resulting in a goiter. About 60 percent of patients with this disorder will develop a goiter at some point in their lives. This disorder may also disrupt balance by affecting the vestibular system. About 40 percent of patients will experience some degree of vestibular weakness when a doctor tests their balance.

When diagnosing this disorder, the doctor will discuss the patient's symptoms with them. Imaging techniques, such as computed tomography or magnetic resonance imaging are often helpful to look for two primary characteristics of this disorder.

There are usually several different specialists involved in treating patients with this disorder, such as an audiologist, clinical geneticist, otolaryngologist, primary care physician, endocrinologist, genetic counselor, and a speech-language pathologist. To help decrease the possibility of hearing loss progressing patients should avoid activities that put them at risk for head trauma. They should also avoid activities in which barotrauma may occur. This condition cannot be cured, but early treatment will help children live the fullest life possible. Cochlear implants are an option to help patients learn a new way to understand speech. Those with a goiter will check in with their doctor often.

Genetics Home Reference. (2008). Pendred Syndrome. Retrieved on November 22, 2010 from Genetics Home Reference: http://ghr.nlm.nih.gov/condition/pendred-syndrome

National Institute on Deafness and Other Communication Disorders. (2006). Pendred Syndrome. Retrieved on November 22, 2010 from the National Institute on Deafness and Other Communication Disorders: http://www.nidcd.nih.gov/health/hearing/pendred.asp